College Algebra (6th Edition)

Published by Pearson
ISBN 10: 0-32178-228-3
ISBN 13: 978-0-32178-228-1

Chapter 1 - Equations and Inequalities - Exercise Set 1.5 - Page 161: 127

Answer

The solutions are $x=-\dfrac{1}{2}\pm\dfrac{\sqrt{21}}{2}$

Work Step by Step

$\dfrac{1}{x^{2}-3x+2}=\dfrac{1}{x+2}+\dfrac{5}{x^{2}-4}$ Factor all the rational expressions present in the equation completely: $\dfrac{1}{(x-1)(x-2)}=\dfrac{1}{x+2}+\dfrac{5}{(x-2)(x+2)}$ Multiply the whole equation by $(x-1)(x-2)(x+2)$: $(x-1)(x-2)(x+2)\Big[\dfrac{1}{(x-1)(x-2)}=\dfrac{1}{x+2}+\dfrac{5}{(x-2)(x+2)}\Big]$ $x+2=(x-1)(x-2)+5(x-1)$ $x+2=x^{2}-2x-x+2+5x-5$ Take all terms to the right side and simplify: $0=x^{2}-2x-x+2+5x-5-x-2$ $0=x^{2}+x-5$ Rearrange: $x^{2}+x-5=0$ Use the quadratic formula to solve this equation. The formula is $x=\dfrac{-b\pm\sqrt{b^{2}-4ac}}{2a}$ In this case, $a=1$, $b=1$ and $c=-5$ Substitute the known values into the formula and evaluate: $x=\dfrac{-1\pm\sqrt{1^{2}-4(1)(-5)}}{2(1)}=\dfrac{-1\pm\sqrt{1+20}}{2}=...$ $...=\dfrac{-1\pm\sqrt{21}}{2}=-\dfrac{1}{2}\pm\dfrac{\sqrt{21}}{2}$
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